JP6560549B2 - Laminated tube and manufacturing method thereof - Google Patents

Description

  The present invention relates to a laminated tube and a manufacturing method thereof.

  As a part used in direct contact with molten metal, for example, a part of a die casting machine for forming a metal is known. The die casting machine is mainly composed of parts such as a plunger, a sleeve, and a molding die, and is used in a state where it is in direct contact with a molten metal (for example, aluminum, zinc, magnesium, etc.). Therefore, the properties required for such parts in common are corrosion resistance to the molten metal, that is, the metal is melted by the molten metal, or a reaction layer is formed on the surface by contact with the molten metal. The characteristic which can prevent this is mentioned.

  Conventionally, it is possible to use tool steel and hot tool steel (such as SKD61) widely used for machine parts as members for parts that are in direct contact with the molten metal, but these members are resistant to corrosion against molten metal. There is a problem that is not enough. In addition, a method of forming a nitrided layer by nitriding the hot tool steel for the purpose of improving the corrosion resistance is also known, but the nitrided layer formed by the nitriding treatment has a thickness of about 20 to 30 μm. Even if this material is used, it is difficult to maintain sufficient corrosion resistance over a long period of time. As described above, when a member having insufficient corrosion resistance is applied to a die casting machine part, it is likely to be deteriorated by molten metal, and such a part must be frequently replaced, and the running cost of the die casting machine is reduced. In addition to the increase, there is a problem that the continuous productivity is significantly decreased.

  On the other hand, a ceramic material (for example, sialon (SiAlON), etc.) having excellent corrosion resistance and high hardness at normal temperature and high temperature is also known as a component member. However, such a ceramic material has a high manufacturing cost and a low workability, and has a higher hardness than necessary. For example, when used as a sleeve of a die casting machine, it is like a plunger tip. When sliding with respect to such a low hardness material, there is a problem that the low hardness material is worn.

  On the other hand, as a component member used in direct contact with such a molten metal, for example, Patent Document 1 has high hardness in a high temperature range, high corrosion resistance against molten metal, and thermal shock resistance. And boride-based tungsten-based alloys having excellent wear resistance (alloys in which a hard phase containing tungsten is dispersed in a binder phase matrix made of a ternary double boride).

Japanese Patent No. 2967789

  However, in the prior art described in Patent Document 1, the boride-based tungsten-based alloy has a sintering temperature as high as 1500 to 2000 ° C., and is sintered while being pressed in a hot press or a predetermined gas atmosphere. In order to form as a part, there is a problem that the productivity is low and the cost is disadvantageous.

  An object of the present invention is to provide a laminated tube which is excellent in corrosion resistance against molten metal and is advantageous in cost.

  The inventors have formed the inner layer by using a first material containing tungsten, and by laminating two layers having predetermined different characteristics on the outer peripheral surface of the inner layer, thereby forming a laminated tube. The inventors have found that this can be achieved and have completed the present invention.

That is, according to the present invention, the first layer made of a boride-based tungsten-based alloy , the second layer made of a ferritic stainless steel material formed on the outer peripheral surface of the first layer, and the outer peripheral surface of the second layer And a third layer made of a martensitic stainless steel material , wherein the second layer has a thickness of 0.1 to 0.9 mm .

In this invention, it is preferable to further provide the chromium molybdenum steel material layer formed in the outer peripheral surface of the said 3rd layer, and being adhere | attached on the said 3rd layer .
In the present invention, the ratio (L / D) of the length L of the laminated tube to the inner diameter D of the first layer is preferably 2 or more.

Further, according to the present invention, a first step of preparing a core material, a second step of spraying a boride-based tungsten-based alloy on the outer peripheral surface of the core material to form a first layer, A third step of spraying a ferritic stainless steel material on the outer peripheral surface of the first layer to form a second layer having a thickness of 0.1 to 0.9 mm ; and a martensite on the outer peripheral surface of the second layer. There is provided a method of manufacturing a laminated tube, which includes a fourth step of spraying a site-based stainless steel material to form a third layer and a fifth step of removing the core material.

In the manufacturing method of the present invention, after the core material is removed by the fifth step, a chromium molybdenum steel material layer is formed by shrink fitting a chromium molybdenum steel material on the outer peripheral surface of the third layer. It is preferable to further include a step.

  In the present invention, the inner layer is formed of the first material containing tungsten, and the second layer and the third layer having predetermined characteristics are formed on the outer peripheral surface of the inner layer. A particularly advantageous laminated tube can be provided.

It is sectional drawing which shows one Embodiment of the die-casting apparatus using the sleeve to which the laminated tube which concerns on this invention is applied. It is a perspective view which shows one Embodiment of the laminated tube which concerns on this invention. It is sectional drawing which shows the layer structure of the laminated tube shown in FIG. It is a figure for demonstrating an example of the method of producing the laminated tube which concerns on this invention. It is a photograph which shows the result of having evaluated the corrosion resistance with respect to the dissolved aluminum alloy about each sample of a reference example. It is a photograph which shows the result of having evaluated the generation | occurrence | production presence or absence of the crack and peeling in each layer about the laminated tube of a reference example and a comparative example. It is a photograph which shows the cross section of the laminated tube of an Example.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. The laminated tube according to the present invention can be used as a component that requires corrosion resistance in a high temperature environment and high hardness. For example, it can be used as a sleeve of a die casting apparatus as shown in FIG. In the following, the present invention will be described in an embodiment in which the laminated tube according to the present invention is used for a sleeve of a die casting apparatus.

  FIG. 1 is a cross-sectional view showing an embodiment of a die casting apparatus 1 using a sleeve 11 to which a laminated tube according to the present invention is applied. The die casting apparatus 1 in this example is a die casting apparatus for forming a molten metal such as aluminum.

  A die casting apparatus 1 shown in FIG. 1 includes a sleeve 11, a plunger 12, a flow path 13, a die cavity 14, a first mold 15, and a second mold 16. The sleeve 11 forms a passage for the plunger 12 to move, and the passage formed by the sleeve 11 is connected to the flow path 13 and the die cavity 14. The plunger 12 reciprocates back and forth in the passage formed by the sleeve 11, and injects the molten metal poured into the sleeve 11 from the sleeve 11 into the die cavity 14 through the flow path 13.

  The sleeve 11 of this embodiment is formed using the laminated tube 2 shown in FIG. FIG. 2 is a perspective view showing an embodiment of the laminated tube according to the present invention. In FIG. 2, the inner diameter of the laminated tube 2 is indicated by D and the length is indicated by L. As shown in the cross-sectional view of FIG. 3, the laminated tube 2 of the present embodiment includes a first layer 21 constituting an inner layer, a second layer 22 formed on the outer peripheral surface of the first layer 21, and a second layer. 22 has a three-layer structure composed of a third layer 23 formed on the outer peripheral surface of 22.

  As shown in FIG. 4, the laminated tube 2 of the present embodiment has a first layer 21 and a second layer 22 by thermal spraying on a core material 3 made of an inexpensive and easy-to-process material such as iron, copper, and aluminum. And after forming the 3rd layer 23 in this order, it can obtain by removing a core material by machining.

<First layer 21>
The first layer 21 constituting the inner layer is made of a first material containing tungsten. An example of the first material is a boride-based tungsten-based alloy. The boride-based tungsten-based alloy is composed of a hard phase mainly made of tungsten and a binder phase mainly made of ternary double boride.

The ternary double boride constituting the binder phase is not particularly limited, but Mo ₂ FeB ₂ , Mo ₂ CoB ₂ , Mo ₂ NiB ₂ , W ₂ FeB ₂ , W ₂ CoB ₂ , W ₂ NiB ₂ , MoCoB , WFeB, WCoB or a mixture of two or more of them can be used.

Further, the binder phase may contain a binary boride in addition to the above-described ternary double boride. As the binary boride, for example, a boride represented by M _x B _y (M is, for example, any one of Ti, Zr, Ta, Nb, Cr, and V, and x = 1 to 2, y = 1. ~ 4.) Or a mixture of two or more of them can be used.

  The content ratio of the binary boride in the binder phase is preferably 1 to 20% by volume, more preferably 3 to 15% by volume. By including the binary boride in the above-mentioned ratio in the binder phase, the hardness of the first layer 21 of the laminated tube 2 obtained is increased in a normal temperature environment and a high temperature environment without impairing the corrosion resistance. Abrasion can be improved.

  Moreover, about the binder phase containing the ternary double boride and binary boride mentioned above, the content rate in the 1st layer 21 becomes like this. Preferably it is 1-30 volume%, More preferably, it is 3-20 volume%. . By setting the content ratio of the binder phase in the first layer 21 to the above ratio, the hardness under normal temperature environment and high temperature environment without damaging the excellent corrosion resistance and toughness of tungsten for the first layer 21 obtained. And the wear resistance, adhesion resistance, thermal shock resistance and workability can be improved.

<Second layer 22>
When the second layer 22 is cooled from a temperature higher than the melting point by 1000 ° C. or higher to 25 ° C. which is room temperature, the second layer 22 is sprayed on the first layer 21 with a property that does not cause transformation accompanied by volume expansion. Can be formed. That is, the second layer 22 is formed of the second material having such a characteristic that the transformation accompanied by expansion does not occur due to the change of the crystal structure and the crystal grain size during the cooling in the above temperature range. Thus, when the second layer 22 is formed on the first layer 21 by thermal spraying, the second material is heated at room temperature from about 2500 ° C., which is a temperature of spraying (that is, a temperature higher than the melting point by 1000 ° C.). In the process of cooling to a certain 25 ° C., the expansion is suppressed, and the occurrence of peeling at the interface between the first layer 21 and the second layer 22 is prevented. In the process of forming the second layer 22, the second material does not necessarily have to be heated to a temperature higher than the melting point by 1000 ° C. or higher and does not need to be cooled to 25 ° C. or lower. For example, in the present embodiment, when the second layer 22 is formed, the second material is melted at a temperature not lower than the melting point and not exceeding 1000 ° C. to perform the thermal spraying. Good. Moreover, in this embodiment, you may hold | maintain the 2nd layer 22 formed by thermal spraying at the temperature higher than 25 degreeC, without cooling to 25 degrees C or less after thermal spraying. In the present embodiment, as the second material, a material having a characteristic that “a transformation accompanied by expansion does not occur when cooled from a temperature higher than the melting point by 1000 ° C. to 25 ° C.” may be used.

  In the present embodiment, by combining such a second layer 22 and a third layer 23 described later, that is, by laminating the second layer 22 and the third layer 23 each having a predetermined different characteristic. The total thickness of the second layer 22 and the third layer 23 in the laminated tube 2 can be increased, whereby the strength of the obtained laminated tube 2 can be improved.

  In the present embodiment, the transformation includes a change in the structure of the material due to a change in crystal structure or crystal grain size. The second material of the present embodiment may be one that does not undergo transformation in the process of cooling in the above temperature range, or one that undergoes transformation if the volume does not substantially expand. . That is, in the second material, the transformation may occur as long as the transformation shrinks in volume or the transformation hardly changes in volume. Alternatively, in the second material, the coefficient of expansion at the time of transformation (expansion coefficient (%) = ((volume after expansion−volume before expansion) ÷ volume before expansion × 100) is 0.03% or less, Any transformation that does not swell may occur.

In the present embodiment, the second material preferably has a thermal expansion coefficient higher than that of the material constituting the first layer 21 and lower than that of the material constituting the core material 3 shown in FIG. 4 described above. For example, when SUS304 or SUS316 is used as the core material 3, the thermal expansion coefficient of SUS304 or SUS316 is about 18 × 10 ⁻⁶ / K (when the second layer 22 is formed, it is heated by the heat of thermal spraying. The thermal expansion coefficient of the second material is preferably less than 18 × 10 ⁻⁶ / K. Thereby, when forming the 2nd layer 22 by thermal spraying, it can prevent that the crack occurs in the 2nd layer 22 in the process in which the 2nd layer 22 is cooled after thermal spraying.

  In the present embodiment, specific materials that can be used as the second material include ferritic steel materials such as SUS430 and SUS429.

<Third layer 23>
The third layer 23 is sprayed on the second layer 22 with a third material having a characteristic that can cause transformation accompanying expansion when cooled from a temperature higher than the melting point by 1000 ° C. or more to a room temperature of 25 ° C. Can be formed. Accordingly, when the third layer 23 is formed on the second layer 22 by thermal spraying, the third material is heated from about 2500 ° C., which is the temperature of thermal spraying (that is, a temperature higher than the melting point by 1000 ° C.). In the process of cooling to 25 ° C., which is room temperature, the third layer 23 is prevented from excessively shrinking with respect to the second layer 22 described above, and cracks are generated in the third layer 23. Can be prevented. Further, the third layer 23 can be formed thicker than the second layer 22. In the process of forming the third layer 23, the third material does not necessarily need to be heated to a temperature higher than the melting point by 1000 ° C. or higher, and need not be cooled to 25 ° C. or lower. For example, in the present embodiment, when the third layer 23 is formed, the third material is melted at a temperature not lower than the melting point and not exceeding 1000 ° C. for spraying. Good. Moreover, in this embodiment, you may hold | maintain the 3rd layer 23 formed by thermal spraying at the temperature higher than 25 degreeC, without cooling to 25 degrees C or less after thermal spraying. In the present embodiment, as the third material, a material having a characteristic that “transformation accompanied by expansion can occur when cooled from a temperature higher than the melting point by 1000 ° C. to 25 ° C.” is used.

  As the third material of the present embodiment, transformation occurs in the process of cooling in the above temperature range, and the expansion rate at the time of transformation (expansion rate (%) = (volume after expansion−volume before expansion)). ÷ The volume before expansion × 100) is 0.8% or more.

In the present embodiment, as the third material, it is preferable that the thermal expansion coefficient is lower than the material constituting the core material 3 shown in FIG. 4 described above. For example, when SUS304 or SUS316 is used as the core material 3, the thermal expansion coefficient of the third material is preferably less than 18 × 10 ⁻⁶ / K as in the second material described above. Thereby, when forming the 3rd layer 23 by thermal spraying, it can prevent that the crack occurs in the 3rd layer 23 in the process in which the 3rd layer 23 is cooled after thermal spraying.

  In the present embodiment, specific materials that can be used as the third material include martensitic steel materials such as SUS420 and SUS403.

  As described above, the laminated tube 2 of the present embodiment is configured.

  Note that the laminated tube 2 of the present embodiment may further include a steel material layer formed by shrink fitting on the outer peripheral surface of the third layer 23. Examples of the steel material layer that is shrink-fitted on the outer peripheral surface of the third layer 23 include a tubular member made of a chromium molybdenum steel material equivalent to SCM440 defined in Japanese Industrial Standard (JIS G 4053). The steel material layer may be fixed to the outer peripheral surface of the third layer 23 by bolt fastening, pins, or the like. Since the laminated tube 2 has a steel material layer, the strength of the laminated tube 2 can be increased.

<Method for producing laminated tube 2>
Next, a method for manufacturing the laminated tube 2 of the present embodiment will be described.

  First, a powder for thermal spraying for forming the core material 3 and the first layer 21 is prepared. The thermal spraying powder can be formed, for example, as follows. First, a tungsten powder that serves as a hard phase and a ternary double boride and a binary boride powder that serve as a binder phase are mixed, and a binder and an organic solvent are added thereto. The mixture is pulverized using a pulverizer such as a ball mill. Next, the powder obtained by mixing and pulverizing (primary particles of several μm) is granulated with a spray dryer or the like to form secondary particles of several tens of μm, and the secondary particles are subjected to heat treatment and classified, Thermal spray powder can be obtained.

  The conditions for heat treating the secondary particles are preferably temperature: 1000-1400 ° C., sintering time: 30-90 minutes, and heating rate: 0.5-60 K / min. When the heat treatment temperature of the secondary particles is lower than 1000 ° C., the bond between the primary particles becomes weak, and the thermal spraying powder tends to collapse during thermal spraying and is not sufficiently accelerated in the thermal spraying frame, so that the adhesion efficiency is lowered. There is a fear. When the heat treatment temperature of the secondary particles exceeds 1400 ° C., the sintering proceeds and the bond between the powders becomes too strong, and it becomes difficult to disintegrate the sintered body and to be taken out as a thermal spraying powder. Become.

  Next, the first layer 21 is formed by spraying the thermal spraying powder prepared as described above on the core material 3. A thermal spraying method for forming the first layer 21 is not particularly limited, but plasma spraying is preferable from the viewpoint of being suitable for thermal spraying of a material having a high melting point.

  Subsequently, the second material described above is prepared, and the second material 22 is sprayed on the first layer 21 to form the second layer 22. Further, the third material 23 is prepared, and the third material 23 is sprayed on the second layer 22 to form the third layer 23. As a result, as shown in FIG. 4, the first layer 21, the second layer 22, and the third layer 23 are formed in this order on the core material 3. The thermal spraying method for forming the second layer 22 and the third layer 23 is not particularly limited, but the second material constituting the second layer 22 and the third material constituting the third layer 23 are not limited. In the case of using the above-described steel material, wire arc spraying is preferable.

  In the present embodiment, a tubular steel material may be shrink-fitted on the outer peripheral surface of the third layer 23 to form a steel material layer. Thereby, the laminated tube 2 can be reinforced and the strength of the laminated tube 2 can be improved.

  Subsequently, the core material 3 is cut using a drilling machine, a BTA (Boring and Trepanning Association) deep hole processing machine, or the like. Accordingly, the core material 3 shown in FIG. 4 is removed, and the laminated tube 2 as shown in FIG. 2, specifically, the inner surface becomes the first layer 21, and the second layer 22 and the third layer are formed on the first layer 21. The laminated tube 2 in which the layer 23 is formed is obtained.

  The laminated tube 2 of this embodiment is manufactured as described above.

  In the laminated tube 2 of the present embodiment, the ratio (L / D) of the length L of the laminated tube 2 to the inner diameter D of the first layer 21 is preferably 2 or more, as shown in FIG. In this case, in particular, the inner diameter D of the first layer 21 is preferably 40 to 160 mm, more preferably 40 to 120 mm. According to the manufacturing method of the present embodiment, the ratio of the inner diameter D to the length L (L / D) is in the above range, and the laminated tube 2 is excellent even when the shape of the laminated tube 2 is relatively elongated. Can be manufactured.

That is, as a method of manufacturing a laminated tube made of a material containing tungsten only for the inner layer, a method of spraying a material containing tungsten on the inner surface of a tubular member prepared in advance can be considered. However, when manufacturing a laminated tube in which the ratio (L / D) of the inner diameter D to the length L is within the above range because the inner diameter D is a small diameter or the length L is long, the tubular There is a problem that the thermal spraying torch does not enter the inside of the member and thermal spraying cannot be performed.
A spraying distance of 100 to 150 mm is appropriate, and even when an inner diameter torch is used, spraying cannot be performed on an inner diameter of 100 mm or less. For this reason, if the inner diameter is 100 mm or less, it must be sprayed at an angle from both ends of the laminated tube. Generally, however, the coating properties are drastically reduced when the spray angle is smaller than 45 °, so that the inner surface of the tube is sprayed. In the case of producing a laminated tube by this method, there is a problem that a high quality sprayed coating cannot be obtained if the L / D is 2 or more.

  On the other hand, in this embodiment, as shown in FIG. 4, after forming the first layer 21, the second layer 22, and the third layer 23 on the core material 3, the inner diameter D is removed in order to remove the core material 3. And a lengthwise L ratio (L / D) in the above range can be produced satisfactorily.

  In the present embodiment, the thickness of the first layer 21 containing tungsten is preferably 0.5 to 2 mm, more preferably 1 to 1.5 mm. By setting the thickness of the first layer 21 in the above range, the obtained laminated tube 2 can be excellent in corrosion resistance against molten metal, and further, the amount of expensive tungsten used can be suppressed and thermal spraying of tungsten can be performed. From the viewpoint that the amount of energy required can be reduced, this is advantageous in terms of cost.

  In the present embodiment, the thickness of the second layer 22 is preferably 0.1 to 0.9 mm. By setting the thickness of the second layer 22 within the above range, it is possible to prevent cracks in the second layer 22 caused by cooling and shrinking after thermal spraying.

  Furthermore, the thickness of the third layer 23 is preferably 1.0 to 5.0 mm. By setting the thickness of the third layer 23 within the above range, the strength of the laminated tube 2 can be increased.

  As described above, the laminated tube 2 of the present embodiment has the first layer 21 containing tungsten as the inner layer and the second layer 22 and the third layer 23 on the first layer 21, and therefore has excellent corrosion resistance against molten metal. In addition, there is a cost advantage. That is, if the entire laminated tube 2 is made of a material containing tungsten (such as a boride-based tungsten-based alloy), the corrosion resistance against the molten metal is improved, but the material containing tungsten is expensive, and the molding process is costly. There is a problem that it takes. On the other hand, in the laminated tube 2 of the present embodiment, only the inner layer is configured by a layer containing tungsten (first layer 21), and the exterior of the first layer 21 is the second layer 22 and the second layer made of steel or the like. Since it is formed of the three layers 23, the corrosion resistance against molten metal can be improved, while it can be manufactured at a relatively low cost. In addition, since the total thickness of the laminated tube 2 of the present embodiment can be increased by the second layer 22 and the third layer 23, the strength of the laminated tube 2 can be improved. Furthermore, by increasing the total thickness of the second layer 22 and the third layer 23, it becomes possible to form a steel material layer on the outer peripheral surface of the third layer 23 by shrink fitting as described above. The strength can be further improved.

  Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to these examples.

<Reference Example 1>
First, the composition of the first layer to be formed is tungsten: balance, binary boride (TiB ₂ ): 5.0% by volume, ternary double boride (Mo ₂ NiB ₂ ): 10.5% by volume. Thus, a thermal spraying powder was prepared. Specifically, B: 0.8% by weight, Mo: 3.5% by weight, Ni: 1.1% by weight, Ti: 0.9% by weight, and W: balance of raw material 100% by weight 5 parts by weight of paraffin was added to the part, and this was pulverized in acetone by a vibration ball mill for 25 hours in acetone. Next, the prepared pulverized powder was dried at 150 ° C. for 18 hours in a nitrogen atmosphere. The dried pulverized powder is mixed with acetone at a weight ratio of 1: 1, and then granulated by a spray dryer. The granulated powder is held at 1100 ° C. in a vacuum for 1 hour to sinter the powder. Then, by classifying this, a powder for thermal spraying of a boride-based tungsten-based alloy was produced.

  Next, 50 × 50 × 10 mm SKD61 steel was prepared as a base material for thermal spraying. And the thermal spray layer of the boride system tungsten base alloy was formed on the base material by spraying the above-mentioned thermal spraying powder with respect to the base material with a plasma spraying machine (NIPPON YUTECH Co., Ltd. EUTRONIC PLASMA SYSTEM 5000). Then, the test piece was produced by processing this into a block shape of 4 mm × 4 mm × 20 mm.

  Subsequently, a graphite mold was prepared, and in the mold, the test piece and an aluminum alloy of ADC12 (Cu: 1.5 to 3.5 wt%, Si: 9.6 to 12 wt, Al: The remainder was added and heated to 700 ° C. in a vacuum to dissolve the aluminum alloy, and kept at 700 ° C. for 1 hour. Next, the test piece and the aluminum alloy are cooled to room temperature, the cooled test piece and the aluminum alloy are cut, the cross section is observed by SEM, and the thickness of the reaction layer formed on the surface of the test piece by the dissolved aluminum alloy Was measured. The results are shown in FIG.

<Reference Example 2>
SKD61 steel (SKD61 nitride material) having a nitrided surface formed by nitriding the surface was processed into a 4 mm × 4 mm × 20 mm block shape, and evaluated in the same manner as in Reference Example 1. The results are shown in FIG.

<Reference Example 3>
The raw material powder was blended so that the composition was B: 4.7% by weight, Mo: 40% by weight, Cr: 8% by weight, Ni: 3% by weight, Fe: balance, and then 100 parts by weight of the raw material powder. On the other hand, 5 parts by weight of paraffin was added, and this was wet-mixed and ground for 25 hours in acetone using a vibration ball mill. Next, the raw material powder subjected to the wet mixing and pulverization was dried in a nitrogen atmosphere at 150 ° C. for 18 hours to obtain a pulverized powder. And the sample which consists of a hard sintered alloy was obtained by press-molding the obtained pulverized powder, and sintering the obtained molded object for 20 minutes at the temperature of 1473-1573K. The heating rate during sintering was 10 K / min. Subsequently, the obtained sample was processed into a block shape of 4 mm × 4 mm × 20 mm to obtain a test piece, which was evaluated in the same manner as in Reference Example 1. The results are shown in FIG.

  As shown in FIG. 5 (A) and Table 1, in Reference Example 1 in which a layer made of a boride-based tungsten-based alloy was formed on the surface, the thickness of the reaction layer formed by the dissolved aluminum alloy was only 8 μm. It was confirmed that the metal was excellent in corrosion resistance against molten metal.

  On the other hand, as shown in FIG. 5 (B), FIG. 5 (C) and Table 1, the reference example 2 which is a SKD61 nitride material and the reference example 3 which is a hard sintered alloy were formed by a molten aluminum alloy. The thickness of the reaction layer was as thick as 70 μm (Reference Example 2) or 130 μm (Reference Example 3), and it was confirmed that the corrosion resistance against molten metal was poor.

<Reference Example 4>
As a core material, a tubular member made of SUS316 and having an outer diameter of 39 mm was prepared. Next, a sprayed layer of a boride-based tungsten-based alloy having the same composition as in Reference Example 1 described above was formed as a first layer on the outer peripheral surface of the prepared core material by plasma spraying. The thickness of the sprayed layer of the boride-based tungsten-based alloy was 1.5 mm. Subsequently, on the first layer, by wire arc spraying, SUS316, which is an austenitic steel material (the thermal expansion coefficient in the temperature range at the time of spraying is as high as about 18 × 10 ⁻⁶ / K, and the temperature of spraying is about 2500. A material that does not undergo transformation with expansion when cooled to 25 ° C., which is room temperature, was sprayed to form a second layer having a thickness of 0.3 mm, and a sample was prepared. About the produced sample, after confirming the presence or absence of generation | occurrence | production of the crack in a 2nd layer, the sample was cut | disconnected and the cross section was observed with the optical microscope, and peeling generate | occur | produced in the interface of a 1st layer and a 2nd layer Observed whether or not. The results are shown in Table 2.

<Reference Example 5>
As the second layer, by wire arc spraying, SUS430, which is a ferritic steel material (the thermal expansion coefficient in the temperature range during spraying is as low as about 10 × 10 ⁻⁶ / K, and the spraying temperature is from about 2500 ° C. to room temperature. A material that does not undergo transformation with expansion when cooled to 25 ° C.) was prepared in the same manner as in Reference Example 4 except that the sprayed layer was formed with a thickness of 1.0 mm. went. The results are shown in Table 2 and FIG.

<Comparative Example 1>
As a second layer, by wire arc spraying, SUS420 which is a martensitic steel material (the thermal expansion coefficient in the temperature range at the time of thermal spraying is as low as about 10 × 10 ⁻⁶ / K, and the thermal spraying temperature is from about 2500 ° C., Samples were prepared in the same manner as in Reference Example 4 except that a thermal sprayed layer of 5.0 mm in thickness was formed except that a material that undergoes transformation with expansion when cooled to 25 ° C., which is room temperature. went. The results are shown in Table 2 and FIG.

  As shown in Table 2, in Reference Example 4 using SUS316 having a relatively high thermal expansion coefficient as the second layer, the second layer had a thickness of 0.3 mm while the second layer was formed by thermal spraying. At that point, a crack occurred.

  Similarly, as shown in Table 2 and FIG. 6A, even when SUS430 having a relatively low thermal expansion coefficient is used as the second layer, while the second layer is formed by thermal spraying. In Reference Example 5 in which the thickness of the second layer was increased to 1.0, cracks occurred in the second layer.

  Furthermore, as shown in Table 2 and FIG. 6 (B), SUS420 was used as the second layer, which has a relatively low thermal expansion coefficient, but undergoes transformation with expansion when cooled from about 2500 ° C. to 25 ° C. In Comparative Example 1, even when the second layer was formed to a thickness of 5.0 mm, no crack was generated in the second layer, but the first layer (boride-based tungsten-based alloy) and the second layer Separation occurred at the interface.

<Example 1>
As a core material, a tubular member made of SUS304 and having an outer diameter of 39 mm was prepared. Next, a sprayed layer of a boride-based tungsten-based alloy having the same composition as in Reference Example 1 described above was formed as a first layer on the outer peripheral surface of the prepared core material by plasma spraying. The thickness of the sprayed layer of the boride-based tungsten-based alloy was 1.5 mm. Next, on the first layer, by wire arc spraying, SUS430 (the thermal expansion coefficient in the temperature range during spraying is as low as about 10 × 10 ⁻⁶ / K, and the temperature of spraying is about 0.5 mm until the thickness becomes 0.5 mm. A material that does not undergo transformation with expansion when cooled from 2500 ° C. to 25 ° C., which is room temperature, was sprayed to form a second layer. And about the formed 2nd layer, the presence or absence of the generation | occurrence | production of a crack was confirmed visually.

Subsequently, on the second layer, by wire arc spraying, SUS420 (the thermal expansion coefficient in the temperature range at the time of spraying is as low as about 10 × 10 ⁻⁶ / K, from about 2500 ° C. which is the temperature of spraying to room temperature. A material that undergoes transformation with expansion when cooled to 25 ° C.) was sprayed to form a third layer having a thickness of 3.5 mm, thereby preparing a sample. For the prepared sample, the presence or absence of cracks in the third layer was confirmed visually, and the sample was cut and the cross section was observed with an optical microscope. The interface between the first layer and the second layer, and the second layer It was observed whether or not peeling occurred at the interface between the first layer and the third layer. The results are shown in Table 3 and FIG.

<Comparative Example 2>
As the second layer, a SUS420 sprayed layer was formed by wire arc spraying until the thickness became 5.0 mm, and a sample was prepared in the same manner as in Example 1 except that the third layer was not formed. evaluated. The results are shown in Table 3.

<Reference Example 6>
As the second layer, SUS304 (the thermal expansion coefficient in the temperature range at the time of thermal spraying is as high as about 18 × 10 ⁻⁶ / K by wire arc spraying, and it was cooled from the thermal spraying temperature of about 2500 ° C. to the room temperature of 25 ° C. In this case, a sample is prepared in the same manner as in Example 1 except that the sprayed layer is formed until the thickness becomes 0.3 mm and the third layer is not formed. Evaluation was performed in the same manner. The results are shown in Table 3.

<Reference Example 7>
As the second layer, a SUS430 sprayed layer was formed by wire arc spraying until the thickness became 1.0 mm, and a sample was prepared in the same manner as in Example 1 except that the third layer was not formed. evaluated. The results are shown in Table 3.

  As shown in Table 3 and FIG. 7, as a material constituting the second layer, a material that does not undergo transformation with expansion when cooled from about 2500 ° C. to 25 ° C. is used. Example 1 using a material that causes transformation with expansion when cooled from about 2500 ° C. to 25 ° C. does not cause cracks in the second layer, and the interface between the first layer and the second layer, No peeling occurred at the interface between the second layer and the third layer. As a result, it was confirmed that the thickness of the second layer and the third layer can be increased while preventing cracks and peeling in the second layer and the third layer, and the strength of the resulting laminated tube can be increased. It was.

  On the other hand, as shown in Table 3, in Reference Example 6 using SUS304 having a relatively high thermal expansion coefficient as the second layer, the second layer had a thickness of 0 while the second layer was formed by thermal spraying. Cracked at 3 mm.

Similarly, as shown in Table 3, even when SUS430 having a relatively low thermal expansion coefficient is used as the second layer, the thickness of the second layer is being formed while the second layer is being formed by thermal spraying. In Reference Example 7 in which the thickness was increased to 1.0, cracks occurred in the second layer.
Furthermore, as shown in Table 3, in Comparative Example 2 using SUS420 in which a transformation accompanied by expansion occurs in the cooling process as the second layer, no cracks are generated even when the second layer is formed to a thickness of 5.0 mm. However, peeling occurred at the interface between the first layer and the second layer.

DESCRIPTION OF SYMBOLS 1 ... Die casting apparatus 11 ... Sleeve 12 ... Plunger 13 ... Flow path 14 ... Die cavity 15 ... 1st metal mold | die 16 ... 2nd metal mold | die 2 ... Laminated tube 21 ... 1st layer 22 ... 2nd layer 23 ... 3rd layer 3. Core material

Claims (5)

A first layer of a boride-based tungsten-based alloy ;
A second layer made of a ferritic stainless steel material , formed on the outer peripheral surface of the first layer;
A third layer formed on the outer peripheral surface of the second layer and made of a martensitic stainless steel material ,
A laminated tube having a thickness of the second layer of 0.1 to 0.9 mm . The laminated tube according to claim 1, further comprising a chromium molybdenum steel material layer formed on an outer peripheral surface of the third layer and fixed to the third layer . The laminated tube according to claim 1 or 2 , wherein a ratio (L / D) of a length L of the laminated tube to an inner diameter D of the first layer is 2 or more. A first step of preparing a core material;
A second step of spraying a boride-based tungsten-based alloy on the outer peripheral surface of the core material to form a first layer;
A third step of thermally spraying a ferritic stainless steel material on the outer peripheral surface of the first layer to form a second layer having a thickness of 0.1 to 0.9 mm ;
A fourth step of thermally spraying a martensitic stainless steel material on the outer peripheral surface of the second layer to form a third layer;
And a fifth step of removing the core material. 6. The method further comprises a sixth step of forming a chromium molybdenum steel material layer by shrink fitting the chromium molybdenum steel material on the outer peripheral surface of the third layer after removing the core material in the fifth step. 4. A method for producing a laminated tube according to 4 .